Two loop engine coolant system

ABSTRACT

This disclosure relates to a coolant system for an internal combustion engine including a turbocharger and an aftercooler. The coolant system comprises an engine loop and an aftercooler loop both loops utilizing a single pump. The engine loop includes the pump, the engine block and head, a first radiator, and a radiator bypass branch. The aftercooler loop includes the pump, the aftercooler, a second radiator, and a radiator bypass branch. Each loop further includes a temperature responsive flow control thermostat for regulating the coolant flow through the associated radiator and/or bypass branch. The thermostat in the aftercooler loop is mounted in the coolant intake line leading to the aftercooler, but it responds to the temperature of the coolant leaving the aftercooler.

Internal combustion engines, such as diesel engines for trucks, areincreasingly being equipped with turbochargers. When running at ratedpower, the turbocharger supplies an increased amount of intake air at apressure boost and thereby improves the engine performance. However, thecompressor of the turbocharger also heats the intake air, and this is adisadvantage when operating at high power output levels. Thisdisadvantage has been partially avoided by providing the engine with anaftercooler which is mounted between the compressor and the intakemanifold. In the usual arrangement, the aftercooler is a liquid cooledheat exchanger that removes some of the heat from the intake air.

Arrangements have proposed wherein the aftercooler is connected in theengine coolant system in order to avoid having two separate liquidcooling systems in an engine. Further, U.S. Pat. No. 3,872,835 andGerman Pat. No. 1,223,196 show engines wherein a single coolant pumpcirculates the engine coolant through the engine block and head, throughan aftercooler, and through engine radiators.

While it is advantageous to cool the air during running conditions, theair should not be cooled at engine start up and during idle or low powerconditions. If the intake air is too cool, problems arise due to noxiousemissions, such as unburnt hydrocarbons and white smoke.

It is a general object of the present invention to provide an improvedtwo-loop engine cooling system that cools the intake air during runningconditions and warms the air during low power conditions. The engineincludes a single coolant pump and two cooling loops, one loop passingthrough the engine block and head and a first radiator and the otherloop passing through the aftercooler and a second radiator. Each loopfurther includes a by-pass branch around the radiator, and a flowcontrol thermostat. The thermostat that regulates the temperature of thecoolant entering the aftercooler, responds to the temperature of thecoolant leaving the aftercooler. During engine warm up and low loadconditions, heat is transferred to the intake air from the coolant, andduring normal running conditions heat is removed from the intake air.

The foregoing and other objects and advantages of the present inventionwill become more apparent from the following detailed description takenin conjunction with accompanying figures of the drawings, wherein:

FIG. 1 is a view of an engine including a cooling system in accordancewith the present invention;

FIGS. 2 through 4 are diagrammatic views illustrating the coolant systemand its operation;

FIG. 5 is a diagrammatic view of an alternative form of the system;

FIG. 6 illustrates a preferred thermostat mounting arrangement.

FIG. 7 illustrates an alternative thermostat mounting arrangement; and

FIG. 8 illustrates a thermostat for use in the system.

While the following description deals with a diesel engine for use, forexample, in a truck, it should be understood that the invention is alsoapplicable to other types of engines.

With reference first to FIG. 1, the engine includes a block 10, a head11 and a crankcase 12. A turbocharger 13 including a turbine 14 and acompressor 15 are provided on one side of the engine, the turbine beingconnected to an exhaust manifold 17 of the engine. The compressor outputis connected to an aftercooler 18, the intake air passing through theaftercooler before flowing to the air intake manifold (not shown) on theopposite side of the engine. The engine further includes a crankshaftthat is connected to turn engine belts 19 which drive a cooling fan 21.An oil cooler and filter assembly 22 is mounted on one side of theengine, the oil cooler being the type, in the specific exampleillustrated and described herein, wherein the coolant is passed throughit in order to cool the oil.

The coolant system includes a pump 26 which is mounted on one side ofthe engine and which is driven by the engine crankshaft, and first andsecond radiators 27 and 28. A plurality of coolant lines or hoseindicated by the numerals 31 through 36 interconnect the parts of thecoolant system. The lines 33 and 34 connect the radiators with the pump26, and the lines 31 and 32 connect the radiators with a flow controlunit 38 and with the passage from the head. The unit 38 is connected bythe line 36 to the pump 26 and by two lines 35 to the aftercooler 18.

The diagrams shown in FIGS. 2 through 4 illustrate the coolant systemand its operation in greater detail. The coolant flow lines are givennumbers different from those in FIG. 1 in order to clarify thedescription of FIGS. 2 through 4.

The engine block 10 and the head 11 include flow passages 40, and theoil cooler 22 is connected to the pump 26 and the passage 40. The inletend of the passage 40 of the block 10 is connected to the outlet of thepump 26 by a line 41, and another line 42 is connected to the outlet ofthe passage 40 and returns the coolant to the intake of the pump 26. Theline 42 has a flow control valve or thermostat 43 connected in it, andthe line 42 is divided into two branches 44 and 45 leading from thethermostat 43. The branch 44 extends from the thermostat 43 directly tothe pump 26 whereas the branch 45 extends through the radiator 27 andthen to the pump intake. The valve 43 is designed in a conventionalmanner to switch at a temperature level of for example, between 205° to220°. At temperatures below this level, the coolant flows from the head11 directly to the pump intake, whereas when the coolant temperature isabove this level, the coolant flows through the radiator 27 before goingto the pump. At temperatures around this level, the thermostat 43modulates and the coolant leaving the head 11 may flow through bothbranches 44 and 45.

Another coolant line 47 connects the outlet of the aftercooler 18 to theintake of the pump 26, and still another line 48 connects the outlet ofthe pump 26 to the inlet of the aftercooler 18. Part of the line 48 isalso divided into two branches 49 and 50, the branch 50 extendingthrough the radiator 28. The branch 49 and the outlet of the radiator 28are connected to a second flow control valve or thermostat 52 whichcontrols the flow of the coolant through the branches 49 and 50 and tothe inlet of the after-cooler 18. In the present example, the thermostat52 is designed to switch at a temperature level of approximately 180°.At temperatures below this level, the thermostat 52 directs the coolantflow from the pump 26 through the bypass branch 49 and to theaftercooler 18. At temperatures above this level the thermostat 52directs the coolant flow through the branch 50 and the radiator 28 andthen to the aftercooler 18.

While the thermostat 52 is connected in the line leading to theaftercooler 18, it is controlled by a temperature sensor 53 that isconnected in the line 47 at the output of the aftercooler 18, andconsequently it responds to the temperature of the coolant leaving theaftercooler 18. The other thermostat 43 of course responds to thetemperature of the coolant entering it.

Thus, the system includes an engine loop and an aftercooler loop, andthe pump 26 is common to both loops. The engine loop includes thepassages 41, 40 and 42, the radiator 27, and the radiator bypass branch44. The aftercooler loop includes the lines 47 and 48, the aftercooler18, the radiator 28, and the radiator bypass branch 49. Most of thecoolant flow is through the engine loop, and the coolant of the twoloops combine and mix in the pump 26. Separate controls 43 and 52 areprovided in the two loops, which hold the temperatures at differenttemperature levels.

FIGS. 2, 3 and 4 illustrate the operation of the cooling system underthree different engine operating conditions. The dashed lines in thesethree figures indicate the paths of flow of the coolant. The pathsindicated in FIG. 2 exist when the engine and the coolant temperatureare relatively low, as when it is being started or warmed up. FIG. 3illustrates the flow paths when the engine and the coolant are warmerthan in the situation shown in FIG. 2, which may occur during low powerconditions of the engine. FIG. 4 illustrates the flow paths when theengine is operating at rated power conditions.

With specific reference to FIG. 2, assume that the engine has just beenstarted and is warming up. The turbocharger 13 is not driven because ofthe absence of a large volume of hot exhaust gases, and consequently theair entering the aftercooler 18 is at essentially ambient temperatureand pressure. The engine and the coolant are also at essentially ambienttemperature. The coolant leaving the pump 26 flows through the engineloop including the line 41, the block 10, the head 11 and the thermostat43. Since the coolant temperature is relatively low and is below theswitching temperature, the thermostat 43 directs the coolant through thebranch 44, thereby bypassing the radiator 27. Consequently, the coolantflowing through the engine block and head is not cooled by the radiator,allowing the engine to warm up quickly.

The coolant leaving the pump 26 also flows through the aftercooler loop.Since the coolant temperature is relatively low and the intake airflowing through the aftercooler 18 is also relatively low, thethermostat 52 directs the coolant flow through the radiator bypassbranch 49. Some of the coolant leaving the head 11 and flowing throughthe branch 44 is pumped into the line 48. As soon as the engine hasstarted and is warming up, the coolant leaving the head 11 is warmed andpart of the warmed coolant leaving the pump 26 enters the branch 49 andflows through the aftercooler 18. This coolant is warmer than theambient air temperature and it heats the intake air flowing through theaftercooler. This is advantageous because the warmed combustion air aidsin the combustion process in the engine cylinders.

FIG. 3 illustrates the flow paths after the engine has warmed up but isoperating at relatively low power. The turbocharger runs at low speedand does not appreciably compress and heat the intake air. The coolantleaving the head 11 of the engine is relatively hot and it is above theswitching temperature of the thermostat 43, and consequently thethermostat 43 directs the coolant to the branch 45 and through theradiator 27. The thermostat 43 modulates and tends to hold the coolanttemperature in the 205° to 220° range by varying the proportions of thecoolant flowing through the two branches 44 and 45. The heated coolantleaving the pump 26 flows through the line 48 and through the branch 49,and it flows through the aftercooler 18 and heats the intake air movingthrough the aftercooler. Sufficient heat is removed by the intake airfrom the coolant in the aftercooler that it is below the switchingtemperature of the thermostat 52, and consequently the thermostat 52directs the coolant through the branch 49 and bypasses the radiator 28.Thus the air is heated by the aftercooler 18 and such heating improvesthe combustion process.

FIG. 4 illustrates the conditions when the engine is operating at ratedpower. The heated coolant from the engine block flows through thethermostat 43 and through the radiator 27 in order to reduce thetemperature of the engine. The thermostat 52 directs the coolant throughthe branch 50 where it is cooled by the radiator 28 and then into theaftercooler 18. The air leaving the turbocharger compressor 15 isrelatively hot but it is cooled as it flows through the aftercooler 18before entering the engine cylinders.

In the specific example being described, the capacity of the radiator 27is much larger than the capacity of the radiator 28 and most of thecoolant flows through the radiator 27. When operating at rated power,the temperature of the coolant leaving the radiator 27 is around 207°.The temperature of the air leaving the compressor of the turbochargerand entering the aftercooler is at approximately 305° to 310°. Assumingthat the coolant is flowing through the branch 50 and the radiator 28,the temperature of the coolant leaving the radiator 28 and entering theaftercooler 18 is at approximately 115°, the temperature having beencooled down from approximately 205° by the radiator 28. The coolantflowing through the aftercooler 18 is heated by the air flowing throughit and the temperature of the coolant flowing past the sensor 53 is atapproximately 180°. The heat removed from the air drops the airtemperature from about 310° to approximately 140°.

Instead of locating the thermostat 52 as shown in FIGS. 1 to 4, it mayinstead be located at the dashed line position 52a shown in FIG. 2 whereit is just upstream of the two branches 49 and 50, and essentially thesame operation will result.

In the alternative form of the invention illustrated in FIG. 5, thecoolant system is generally similar to that illustrated in FIGS. 1through 4, and therefore the same reference numerals are employed toindicate the engine block and head 10 and 11, the aftercooler 18, theradiators 27 and 28 and the pump 26. The difference between the FIG. 5system and the previously described system is that another line 62 isconnected in parallel with and upstream of the branches 49 and 50. Theline 62 includes a third flow control valve or thermostat 63 that islocated between the outlet of the pump 26 and the two branches 49 and50. The thermostat is designed to switch at a lower temperature, such asabout 160° F., than the thermostat 52. When the temperature of thecoolant leaving the pump 26 is lower than this temperature, all of thecoolant is directed through the line 62 and the two branches 49 and 50are bypassed. Thus, the thermostat 63 ensures that no coolant will flowthrough the radiator 28 while the engine temperature is low, and itprevents overcooling of the engine. A check valve 64 is preferablyconnected in the line 49 to prevent reverse flow of the coolant when thethermostat 63 is open. Instead of connecting the thermostat 52 at thelocation shown in solid lines in FIG. 5, it could instead be located atthe dashed line position indicated by the numeral 52a.

FIG. 6 illustrates the preferred construction of a control unit 38 whichmay be used in either of the foregoing forms of the invention. The unit38 includes a housing 71 forming a flow chamber 72. A hose or tubeconnector 73 is attached to the housing 71 for connecting the chamber 72with the outlet of the aftercooler, so that the coolant leaving theaftercooler flows through the chamber 72. At the other end of thehousing 71 is formed an outlet 74 which is adapted to receive a tube(not shown in FIG. 6) for connecting the chamber 72 to the intake of thepump. Thus, the coolant leaving the aftercooler flows through thechamber 72 and then to the pump.

If desired, an engine accessory such as an air compressor may also beconnected in the line between the aftercooler and the pump and in serieswith the chamber 72. The statement that the chamber 72 receives thecoolant flow from the aftercooler and that the sensor 52 responds to thetemperature of the coolant leaving the aftercooler is considered toinclude the arrangement where an accessory is connected in the linebetween the connector 73 and the aftercooler as mentioned above. If suchan accessory does not appreciably change the temperature of the coolantflowing through it, the temperature of the coolant entering the chamber72 is essentially that of the coolant leaving the aftercooler. Forexample, if the coolant is passed through the head of an air compressorof the engine, the coolant will be heated only by about 0.5° F., andthus it has a minimal effect on the operation of the coolant system.

Attached to one side of the housing 71 is a thermostat casing 76 thathouses the thermostat 52 and the sensor 53. The thermostat 52 includes atubular movable sleeve 77 and a flange 78 that is secured betweenadjoining surfaces of the housing 71 and the casing 76. The thermostat52 is mounted in openings 79 formed in the casing 76 and the housing 71,and the sensor 53 extends through the openings 79 and into the chamber72. Consequently, the coolant flowing through the chamber 72 flowsaround the sensor 53. The sleeve 77 is supported by a rod 80 and aspider 80a. The rod 80 extends down the center of the sleeve and it issupported by the flange 78, and the spider 80a is secured to the rod 80and to the inner surface of the tubular sleeve 77. The rod 80 isconnected to and is moved by the sensor 53. As an example, the sensor 53may contain a quantity of wax that melts at the switching temperature ofthe thermostat. When the coolant temperature rises above the switchingtemperature, the wax melts and expands, and this expansion moves the rod80 and the sleeve 79 to the left to the position shown in dashed linesin FIG. 6. When the coolant temperature drops, the wax solidifies andshrinks, and a return spring (not shown) in the sensor moves the rod 80and the sleeve toward the right to the position shown in solid lines inFIG. 6. Thus, the sleeve 77 is movable toward and away from the sensor53, relative to the flange 78 and the casing 76.

Generally coaxial with the sleeve 77 and with its axis of movement is anopening 81 which is adapted to receive a tube 82 that is also attachedto the inlet of the aftercooler. The casing 76 has two additional flowopenings 83 and 84 formed in it, the opening 83 being coupled to theoutput of the pump 26 and the line 49 and the opening 84 being coupledto the radiator 28 outlet. The openings 83 and 84 respectively connectwith flow chambers 86 and 87 formed in the casing 76, the chambers 86and 87 being separated by a wall 89. The sleeve 77 extends through ahole 91 formed in the wall 89 and an O-ring 92 forms a seal between thewall 89 and the sleeve 77.

When the sleeve 77 is in the solid line position shown in FIG. 6, thecoolant flows from the chamber 86 and through the space between the leftend of the sleeve 77 and the adjacent side of the casing 76. When thesleeve 77 is in the dashed line position, the coolant flows from thechamber 87, through the space between the right hand end of the sleeveand the flange 78, and through the center of the sleeve. When the sleeveis intermediate the two positions shown, there is flow from both of thechambers 86 and 87 to the line 82. Thus, the aftercooler outlet coolanttemperature controls the proportions of the coolant flowing from the twoopenings 83 and 84 to the opening 81 and, eventually, to theaftercooler.

FIGS. 7 and 8 illustrate another construction of a flow control unit 96which is usable in any of the foregoing systems. With reference to FIG.7, the control unit 96 includes a housing formed by two parts 97 and 98for a thermostat 99. The thermostat 99 includes an annular flange 101that is clamped between the two parts 97 and 98, bolts 102 beingemployed to secure the housing parts together. An O-ring 103 forms aseal between the two parts. The housing part 97 forms a chamber 104, andcoolant flows from an inlet 106, through the chamber 104, and to anoutlet 107. The housing part 98 includes an inlet opening 111, a firstoutlet 112 and a second outlet 113. An internal wall 114 separates thetwo outlets 112 and 113. A member 116 is secured to the part 98 over theinlet 111, and a passage 117 of the part 116 feeds coolant to theinterior of the part 98. Means such as a gasket 118 is provided to sealthe joint between the parts 98 and 116.

When connected in the system shown in FIG. 2, the inlet 106 is connectedto the aftercooler 18 outlet and the outlet 107 is connected to theintake of the pump 26. The passage 117 receives coolant from the pump 26outlet line 48, the outlet 113 is connected to the line 50 leading tothe radiator 28, and the outlet 112 is connected to the intake of theaftercooler 18. Thus the unit 96 shows the thermostat 99 connected inthe location indicated by the dashed line thermostat 52a in FIG. 2.

The thermostat 99 shown in FIGS. 7 and 8 includes a solid conical wall121 that has the flange 101 formed at its outer edge. A sensor 122 ismounted at the center of the wall 121 and extends into the chamber 104.A rod 123 is connected to the sensor 122 and extends axially of thethermostat, and a spider 124 is secured to the other end of the rod 123.A hollow cylindrical part 126 is supported by the spider 124 andsurrounds the rod 123 and a coiled spring 127 which urges the part 126toward the right as seen in FIGS. 7 and 8.

With reference to FIG. 7, the sensor 122, when relatively hot, moves therod 123, the spider 124 and the part 126 toward the left to the dashedline position. In this position, the left end surface 128 of the part126 engages a right end surface 129 of the part 116. In this position,the right end surface 129 of the part 126 is spaced from the wall 121and an opening 131 is formed between the parts 121 and 126.

When the sensor 122 is relatively cool, the part 126 is in the solidline position shown in FIG. 7 where the surface 129 engages the wall 121and an opening 132 is formed between the the surfaces 128 and 129.

Thus, the aftercooler outlet temperature operates the sensor 122 whichin turn moves the part 126. When the sensor 122 is hot, the coolantflows from the inlet 117, through the space 131 and to the outlet 113,and when the sensor 122 is relatively cool the coolant flows through thespace 132 to the outlet 112. Of course, the part 126 may also be inintermediate positions so that the flow is directed to both outlets 112and 113.

It will be apparent from the foregoing that the apparatus describedherein is highly advantageous. Even though only one engine driven pumpis required, the apparatus provides coolant flow through two loops, oneloop being at one temperature and including the engine block and theother loop being at another temperature and including the aftercooler.The arrangements described herein make it possible to heat the intakeair at light loads and to cool the intake air at higher engine loads andtemperatures. This results in improved engine performance and in reducednoxious emissions. The coolant temperature at the outlet of theaftercooler 18 is influenced both by the temperature of the coolantflowing through the aftercooler and by the temperature of the intake airflowing through the aftercooler. Consequently, the thermostat 52 is maderesponsive to both the coolant temperature and the air temperature byreason of the sensor 53 being at the outlet of the aftercooler. In thepresent arrangement, at light loads the system attempts to hold thecoolant temperature at the aftercooler outlet at a relatively constantvalue. The system cools the intake air at rated load but neverthelessthe coolant does not cool the intake air but instead warms it. Byproviding separate loops and a control in each loop, it is possible tokeep the engine hot while adjusting the air cooling requirements.

I claim:
 1. A coolant system for an internal combustion engine includingan aftercooler for cooling the intake air flowing into the engine, saidaftercooler having a coolant intake and a coolant outlet, and saidengine including a block and a head, said coolant system comprising anengine loop and an aftercooler loop, a pump having an output, both ofsaid loops including said pump, said engine loop including said pump,the engine block and head, a first radiator, and a first radiatorbypass, said aftercooler loop including said pump, said intake of theaftercooler being connected to said output of said pump, a secondradiator and a second radiator bypass connected to said inlet of saidaftercooler, each of said loops further including a temperatureresponsive flow control thermostat for regulating the coolant flowthrough the associated radiator and said bypass, said thermostat in saidaftercooler loop including a sensor located in said coolant outlet tosense the temperature of the coolant leaving said aftercooler. 2.Apparatus as in claim 1, wherein said second radiator and said secondradiator bypass are connected in parallel and are connected between theoutput of said pump and said coolant intake of said aftercooler. 3.Apparatus as in claim 2, wherein said thermostat of said aftercoolerloop is connected between said coolant intake of said aftercooler andsaid parallel connection of said second radiator and said secondradiator bypass.
 4. Apparatus as in claim 2, wherein said thermostat ofsaid aftercooler loop is connected between said output of said pump,said parallel connection of said second radiator and said secondradiator bypass.
 5. Apparatus as in claim 1, wherein said thermostat ofsaid engine loop includes temperature responsive means for switching ina preset temperature range, and said thermostat of said aftercooler loopincludes temperature responsive means for switching in a presettemperature range that is lower than said temperature range of saidthermostat of said engine loop.
 6. Apparatus as in claim 1, and furtherincluding a coolant flow passage in said aftercooler loop, said passagebeing in parallel with and upstream of said second radiator and saidsecond radiator bypass, and a third thermostat connected in saidpassage, each of said thermostats switching at a preset temperaturerange, and said range for said third thermostat being lower than saidranges for the other of said thermostats.
 7. Apparatus as in claim 1,wherein said engine loop includes flow passages and said intercoolerloop includes flow passages, and the flow capacity of said passages ofsaid engine loop are substantially greater than the flow capacity ofsaid passages of said aftercooler loop.
 8. A coolant system of aninternal combustion engine including an aftercooler, said systemcomprising a coolant pump, coolant flow lines connecting the intake andoutlet of said pump with the intake and outlet of said aftercooler,whereby the coolant is pumped in a loop including the aftercooler, thepump, and said flow lines, one of said lines being formed by a radiatorbranch and by a bypass branch in parallel with said radiator branch,said system further including a temperature responsive flow controlthermostat connected to said branches at said intake of said aftercoolerfor regulating the coolant flow through said radiator branch and saidbypass branch, said thermostat including a sensor located to respond tothe temperature of the coolant adjacent the outlet of said aftercooler.9. A coolant system as in claim 8, wherein said branches are in saidline between said pump outlet and said aftercooler intake.
 10. A coolantsystem for an internal combustion engine having an aftercooler, theengine and the aftercooler having coolant flow passages therein, saidcoolant system comprising:(a) a coolant pump including an intake andoutlet, (b) a first line connecting said pump outlet with the enginepassages, (c) a second line connecting the engine passage with the saidpump intake, said second line comprising first and second branches, afirst heat exchanger connected in said first branch, first valve meansconnected in said second line for controlling the flow of coolantthrough said first and second branches, said first valve meansresponding to the coolant temperature in said second line and directingcoolant through said first branch at elevated temperatures and directingcoolant through said second branch at reduced temperatures, (d) a thirdline connecting said pump intake with an outlet end of said aftercooler,and (e) a fourth line connecting said pump outlet with the inlet end ofsaid aftercooler, said fourth line comprising third and fourth branches,a second heat exchanger connected in said third branch, second valvemeans connected in said fourth line for controlling the flow of coolantthrough said third and fourth branches to said inlet end of saidaftercooler, said second valve means including sensor means respondingto the coolant temperature leaving said outlet end of said aftercoolerand directing coolant flow through said third branch at elevatedtemperatures and directing coolant flow through said fourth branch atreduced temperatures.
 11. An internal combustion engine comprising ablock and head having combustion chambers and coolant passages therein,a pump, a first radiator and a first radiator bypass, flow linesconnecting said pump with said passages, said radiator and said radiatorbypass, a turbocharger connected to supply intake air to the combustionchambers of said engine, first temperature responsive flow control meansconnected to regulate the flow of coolant through said first radiatorand said first radiator bypass, an aftercooler mounted in the intake airflow path between said turbocharger and said chambers, coolant flowpassages in said aftercooler and said passages including an intake andan outlet, a second radiator and a second radiator bypass, flow linesconnecting said pump with said aftercooler, said second radiator, andsaid second radiator bypass, and second temperature responsive flowcontrol means connected in said intake to regulate the flow of coolantthrough said second radiator and said second radiator bypass, saidsecond flow control means including sensor means connected in saidoutlet and responsive to the temperature of the coolant leaving saidaftercooler.